• The Earth’s Atmosphere:

    In which layer do planes fly?

An atmosphere is a gaseous envelope that covers a planet. In our case, the Earth’s atmosphere is divided into several layers and contains the gases necessary for life to exist.

In addition, our atmosphere absorbs ultraviolet radiation from the Sun, reduces the thermal oscillation between day and night, and acts as an effective shield to deflect meteors and other space debris.

Its composition is based on 78% nitrogen, which is essential for plant life; 21% oxygen, which is necessary for breathing; and the remaining 1% is made up of the other gases, including neon, argon, hydrogen and carbon dioxide.

Did you know that the atmosphere also contains water vapour, which is responsible for meteorological phenomena?

The five layers of the atmosphere

The atmosphere begins at ground level and reaches up to an altitude of 1,000 kilometres, or 540 nautical miles. In addition, it is not homogeneous across its vast expanse, which is why we divide it into five different layers, each with its own peculiarities.

  1. Troposphere: The lowest layer of all. This is where meteorological phenomena take place.
  2. Stratosphere: It contains the ozonosphere, or ozone layer, which absorbs up to 99% of ultraviolet radiation.
  3. Mesosphere: This is the coldest layer of the earth’s atmosphere and is also where atmospheric turbulence and waves originate.
  4. Thermosphere: Also called the ionosphere, it is the layer in which the higher the altitude, the higher the temperature.
  5. Exosphere: The most distant layer of all, with an upper limit of 1000 km.

In addition, the separations between layers are named with the suffix ‘pause’: tropopause, stratopause, mesopause and thermopause, in order of proximity to the earth’s surface.

The Troposphere

The troposphere, the lowest layer of the earth’s atmosphere, extends up to an average altitude of 12 km, up to 6 km at the poles and up to 20 km in the tropics.

It is home to humans and all of the Earth’s biodiversity. Of course, it is also the layer in which birds fly.

The troposphere is the layer in which all meteorological phenomena originate and is also the layer used by aviation.

The Stratosphere

The stratosphere extends from about 12 to 50 kilometres above sea level. Unlike the troposphere, the higher the altitude, the higher the temperature in this layer.

But the most important thing about the stratosphere is that it contains the ozone layer, also known as the ozonosphere. This layer contains 90% of all ozone gas in the atmosphere and is capable of neutralising up to 99% of high-frequency ultraviolet rays.

Finally, the stratosphere is where some military aircraft flights pass through, and also where the International Space Station is located.

The Mesosphere

The mesosphere, the coldest layer of the Earth’s atmosphere, begins at an altitude of 50 kilometres and extends to about 80 kilometres. Temperatures here can range from -80 ºC to -90 ºC.

This layer contains only 0.1% of the total air, which causes the creation of atmospheric waves and turbulence, sensitive on a large space-time scale.

The Thermosphere

Also known as the ionosphere, the thermosphere is the layer we use for radio transmissions. And it is here that we find communication and navigation satellites.

The thermosphere extends from approximately 80 km to 700 km altitude. It is also the location of the Kármán Line, which is considered the boundary between the atmosphere and outer space in aviation terms.

The Exosphere

The exosphere is the last layer of the Earth’s atmosphere and extends from 700 km to 1000 km, although it is considered to be relatively boundless. It is characterised by its low density, consisting mostly of hydrogen and helium.

The temperature, the most extreme of all, ranges from 2500 °C to -273 °C, which is considered the lowest possible temperature, also called absolute zero.

In which layer of the atmosphere do aeroplanes fly?

Now that you are clear about the particularities of each of the layers of the Earth’s atmosphere, you may be wondering in which layer do aeroplanes fly. Although we’ve already given you some background, we’ll expand on the subject below.

The layer in which aircraft fly is the troposphere, the layer closest to the Earth, although within this layer, each type of aircraft uses a different altitude depending on its needs.

For example, school flights, as well as private flights in general, always remain in the troposphere. This is because it is necessary to maintain visual references with the terrain, and piston engines need oxygen to operate.

Commercial aircraft, on the other hand, use the upper reaches of the troposphere. This allows them to take advantage of the low air density to achieve higher speeds and lower fuel consumption. In addition, this altitude is free of intense weather phenomena and birds.

Finally, military flights use the area between the troposphere and the stratosphere, known as the tropopause. In this layer, the density is even lower, so their jet engines are at their most efficient.

Pilots need to know the atmosphere inside out

It is essential that all pilots know and understand the earth’s atmosphere, as much of their time will be spent flying from place to place through it.

Knowledge of the atmosphere will enable them to predict and understand the behaviour of the aircraft in flight, and they will be able to adjust routes and altitudes more efficiently to avoid turbulence and severe weather.